Bacterial Community Structure and Antibiotic Resistance Gene Changes in IFAS+Magnetic Coagulation Process Wastewater Treatment Plant in Cold Regions

Abstract

The main objective of this study was to explore the changes in bacterial communities and antibiotic resistance genes (ARGs) in an integrated fixed-film activated sludge (IFAS)+magnetic coagulation process wastewater treatment plant (WWTP) in Xinjiang. The bacterial communities and ARGs in the influent, suspended activated sludge, attached biofilm, and effluent were studied using 16S rRNA gene sequencing and metagenomic sequencing. The results showed that the average relative abundances of Chloroflexi and Nitrospirae in activated sludge were 3.50% and 0.03%, respectively, and their relative abundances in biofilm reached 10.02% and 2.12%, respectively. The average removal rates of NH4+-N and TN increased from 91.89% and 66.76% to 97.71% and 91.90% after the reformation of this wastewater treatment plant, respectively, indicating that IFAS enhanced the biological nitrogen removal capacity of wastewater treatment plants in cold regions. The average relative abundances of Ferruginibacter and Rhodoferax related to iron redox in the biological treatment section were 5.24% and 3.72%, respectively, and the relative abundance of Rhodoferax in effluent reached 9.48%, indicating that the magnetic powder had an impact on the bacterial community. The IFAS wastewater treatment plant had an obvious removal effect on ARGs, and the relative abundance of ARGs decreased from 191.08×10-3‰ in the influent to 32.58×10-3‰ in the effluent. The relative abundance of ARGs in activated sludge was 63.25×10-3‰-72.38×10-3‰, which was significantly higher than 41.31×10-3‰ in biofilm. However, the relative abundances of dominant subtypes of ARGs such as sul2, floR, and rpoB2 in biofilm were 5.77×10-3‰, 2.52×10-3‰, and 2.03×10-3‰, respectively, which were higher than the 3.15×10-3‰-3.57×10-3‰, 1.73×10-3‰-2.24×10-3‰, and 1.28×10-3‰-1.76×10-3‰ in activated sludge. The network analysis indicated that Caldilineaceae_norank and Trichococcus were respectively positively correlated with sul2 and floR. These results can provide theoretical reference for the optimal operation and ARGs control of WWTPs in cold regions.